App.js

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 * @flow
 */

import React, {Fragment} from 'react';
import {
  Alert,
  SafeAreaView,
  StatusBar,
  StyleSheet,
  Text,
  View,
} from 'react-native';

import {Header, Colors} from 'react-native/Libraries/NewAppScreen';
import {LoginButton, AccessToken} from 'react-native-fbsdk';

const App = () => {
  return (
    <Fragment>
      <StatusBar barStyle="dark-content" />
      <SafeAreaView>
        <Header />
        {global.HermesInternal == null ? null : (
          <View style={styles.engine}>
            <Text style={styles.footer}>Engine: Hermes</Text>
          </View>
        )}
        <View style={styles.body}>
          <View style={styles.sectionContainer}>
            <Text style={styles.sectionTitle}>Step One</Text>
            <Text style={styles.sectionDescription}>
              Edit <Text style={styles.highlight}>App.js</Text> to change this
              screen and then come back to see your edits.
            </Text>
          </View>
          <View
            style={[styles.sectionContainer, styles.facebookButtonContainer]}>
            <LoginButton
              onLoginFinished={(error, result) => {
                if (error) {
                  Alert.alert('Login has error', result.error);
                } else if (result.isCancelled) {
                  Alert.alert('', 'Login is cancelled by user');
                } else {
                  AccessToken.getCurrentAccessToken().then(data => {
                    Alert.alert('', 'Logged in successfully');
                  });
                }
              }}
              onLogoutFinished={() =>
                Alert.alert('', 'Logged out successfully')
              }
            />
          </View>
        </View>
      </SafeAreaView>
    </Fragment>
  );
};

const styles = StyleSheet.create({
  engine: {
    position: 'absolute',
    right: 0,
  },
  body: {
    backgroundColor: Colors.white,
  },
  sectionContainer: {
    marginTop: 32,
    paddingHorizontal: 24,
  },
  sectionTitle: {
    fontSize: 24,
    fontWeight: '600',
    color: Colors.black,
  },
  sectionDescription: {
    marginTop: 8,
    fontSize: 18,
    fontWeight: '400',
    color: Colors.dark,
  },
  highlight: {
    fontWeight: '700',
  },
  facebookButtonContainer: {
    alignItems: 'center',
    paddingBottom: 24,
  },
  footer: {
    color: Colors.dark,
    fontSize: 12,
    fontWeight: '600',
    padding: 4,
    paddingRight: 12,
    textAlign: 'right',
  },
});

export default App;